manfull.pl: Avoid silent failures

* mk/manfull.pl: Report failures of patching of single-page HTML
manuals.

It should prevent silent generating of manual pages inconsistent with
provided CSS files when output of makeinfo will change next time.

mk/manfull.pl

@@ -1,11 +1,14 @@
 #!/usr/bin/perl
 
+$failures = 0;
 
 while ($page = shift) {
 system "mv $page $page.orig";
 open IN,"<$page.orig" or die "Cannot read from $page.orig\n";
 open OUT,">$page" or die "Cannot write to $page\n";
 
+$toc = undef;
+
 while (<IN>) {
   if (/<meta http-equiv="Content-Style-Type" content="text\/css">/) {
     print OUT;
@@ -25,4 +28,11 @@ while (<IN>) {
   }
 }
 system "rm $page.orig";
+
+if (!defined($toc) || $toc != 0) {
+  ++$failures;
+  print STDERR "Patching of $page failed\n";
 }
+}
+
+$failures == 0 or die "Patching of $failures files failed\n";